Quick Read – 2 minutes
Every day the human body loses around 1.7 litres of fluid going to the toilet and 0.5 litres through sweating. Fluid is also lost just by breathing. Water plays several key roles in the body, such as removing waste products in urine, lubricating joints, transporting nutrients around the body, and controlling temperature. It's important to replace lost fluid for your body to function properly, by drinking and eating foods that contain water to prevent dehydration (see How Food Contributes to Daily Fluid Intake).
As a basic guide, the NHS recommends up to 1.2 litres of fluids a day. A medium glass is about 200ml, which means drinking about six to eight glasses of fluid a day.
Below are factors that may affect necessary fluid intake.
Exercise - when carrying out an activity that makes you sweat, extra fluid needs to be consumed to replace the water loss. It's recommended to drink sips of water before, during and after exercise.
Environment - humid or hot weather can cause the body to sweat and need additional fluid. Dehydration can also occur at high altitudes due to drier air which removes fluid from the lungs.
General health - the body loses fluids when vomiting, showing a high temperature, or diarrhoea. In these circumstances, it is often recommended to drink more water or drink oral rehydration solutions. Bladder infections and urinary tract stones are other examples of conditions that might require increased fluid intake.
Pregnancy or breastfeeding - if pregnant or breastfeeding you may need additional fluids to stay hydrated. The additional water aids digestion, supports increasing blood volume, and helps to form amniotic fluid.